1. Field of the Invention
The present teachings relate to methods of producing tungsten-containing nanoparticles, including tungsten-containing nanoparticles with an average particle size of less than about 5 nanometers. The methods include hydrolyzing or precipitating tungsten-containing components to form nanoparticles in a reverse microemulsion, collecting or precipitating tungsten-containing nanoparticles from a reverse microemulsion, and calcining the tungsten-containing nanoparticles to the desired tungsten required valence state.
2. Discussion of the Related Art
The high surface to volume ratio of nanoparticles, particles with diameters between about 1 and about 100 nanometers, makes them of interest for various uses including magnetic, electronic, catalytic, and pigment applications. Assorted preparative methods including both physical and chemical approaches are known.
Various chemical processes that produce metal or metal oxide-containing nanoparticles utilizing microemulsions and reverse microemulsions are known. See, for instance, U.S. Pat. Nos. 6,869,584 B2; 5,725,802; 5,670,088; and 5,695,901. None of these references teach or suggest any method of forming tungsten or tungsten oxide-containing nanoparticles, including by means of a microemulsion or a reverse microemulsion.
It is known to utilize a reverse microemulsion as a means of providing aqueous nandroplets as nanoreactors or nano-domains, wherein the reaction to form the desired product can be carried out. The aqueous nanodroplets can be stabilized in the non-aqueous (or non-polar) phase through the use of surfactants, and the size of the nanodroplets can control or influence the particle size of the product produced therein.
With respect to tungsten and/or tungsten oxide nanoparticles, a need exists for methods of producing tungsten and/or tungsten oxide nanoparticles with average particle size of less than about 10 nanometers, preferably less than about 5 nanometers.